title: Oral administration of corn zein hydrolysate stimulates GLP-1 and GIP secretion and improves glucose tolerance in male normal rats and Goto-Kakizaki rats.
abstract: We have previously demonstrated that ileal administration of the dietary protein hydrolysate prepared from corn zein (ZeinH) stimulated glucagon-like peptide-1 (GLP-1) secretion and attenuated hyperglycemia in rats. In this study, to examine whether oral administration of ZeinH improves glucose tolerance by stimulating GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) secretion, glucose tolerance tests were performed in normal Sprague-Dawley male rats and diabetic Goto-Kakizaki (GK) male rats. The test solution was gavaged before ip glucose injection in normal rats or gavaged together with glucose in GK rats. Blood samples were collected from the tail vein or by using the jugular catheter to measure glucose, insulin, GLP-1, and GIP levels. In the ip glucose tolerance test, oral administration of ZeinH (2 g/kg) significantly suppressed the glycemic response accompanied by an immediate increase in plasma GLP-1 and GIP levels in normal rats. In contrast, oral administration of another dietary peptide, meat hydrolysate, did not elicit a similar effect. The glucose-lowering effect of ZeinH was attenuated by a GLP-1 receptor antagonist or by a GIP receptor antagonist. Furthermore, oral ZeinH induced GLP-1 secretion and reduced glycemic response in GK rats under the oral glucose tolerance test. These results indicate that the oral administration of the dietary peptide ZeinH improves glucose tolerance in normal and diabetic rats by its incretin-releasing activity, namely, the incretinotropic effect.
authors.affiliation: Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Higuchi
authors.forename: Tohru
authors.initials: T
authors.lastname: Hira
authors.forename: Nao
authors.initials: N
authors.lastname: Yamada
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hara
mesh_terms: D000818:Animals; D002460:Cell Line; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000178:diet therapy* / Q000378:metabolism; D019587:Dietary Supplements; D004063:Digestion; D020895:Enterocytes / Q000187:drug effects / Q000378:metabolism*; D005749:Gastric Inhibitory Polypeptide / Q000037:antagonists & inhibitors / Q000097:blood / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1 / Q000037:antagonists & inhibitors / Q000097:blood / Q000378:metabolism*; D000067757:Glucagon-Like Peptide-1 Receptor; D005951:Glucose Tolerance Test; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000627:therapeutic use*; D008297:Male; D051379:Mice; D011492:Protein Hydrolysates / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000627:therapeutic use*; D051381:Rats; D011919:Rats, Inbred Strains; D017207:Rats, Sprague-Dawley; D011964:Receptors, Gastrointestinal Hormone / Q000037:antagonists & inhibitors / Q000378:metabolism; D018027:Receptors, Glucagon / Q000037:antagonists & inhibitors / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D015028:Zein / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000627:therapeutic use*
chemical_list: C000593834:Glp1r protein, mouse; C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D007004:Hypoglycemic Agents; D011492:Protein Hydrolysates; D011964:Receptors, Gastrointestinal Hormone; D018027:Receptors, Glucagon; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; D015028:Zein; C041086:gastric inhibitory polypeptide receptor